Modifications of flow properties may be observed when injected brine replaces formation water, especially when the salinity of the injected brine is lower than the resident one. This is generally attributed to detrimental physico-chemical rock/fluid interactions such as ion exchanges. This paper concerns ion exchange mechanisms related to permeability damage.
A laboratory study conducted in batch and flow conditions relates the permeability reduction to the physico-chemical rock interaction. Batch experiments aim to determine the Critical Salt Concentration (CSC) for clay deflocculation. Flow experiments show the effect of pH and water composition on the permeability reduction in a transient region resulting from ion exchanges. These experiments are represented by a flow model involving ion exchange, CSC and permeability reduction. The modeling of the physico-chemical interaction in flow conditions compares very well with experimental results in a wide range of situations.
A 3D chemical model including two phase flow and physico-chemical equilibria is presented for extrapolating laboratory data to reservoir scale. The numerical study evaluates the effect of the composition of both the resident brine and the injected solution on the resulting properties of the reservoir.
The conclusions obtained from the simulations enabled us to deduce different strategies for optimizing well treatment or water injection. It is shown that detrimental permeability effects can be avoided by adjusting the water compositions.